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In present work, the radiation propagation in atmosphere from laser source to the receiver is considered by taking into account deviations of optical beam due to turbulence. The photon flux density on the receiver has been evaluated.

The separation coefficients of ZrF4(HfF4) and metal fluoride impurities in the process of vacuum sublimation between 900 and 1200 K in the molecular vaporization regime were calculated. The separation coefficients were found to decrease in the order CrF2> MnF2> NiF2> CoF2> MnF3> FeF2> AlF3> CrF3> CuF2> FeF3 . The conditions for purification of ZrF4and HfF4by vacuum sublimation were optimized. The total impurity content in both fluorides was found to increase with the product of the evaporation rate per unit area and the degree of evaporation. Fe was found to be the most difficult-to-remove impurity in ZrF4and HfF4 . The production rate of the sublimating plant is about 100 kg/year of ZrF4and HfF4sublimates. ZrF4was used to prepare optical fibers for laser applications and noncontact fiber sensors for monitoring the composition and temperature of liquid radioactive waste. Fluorohafnate glasses were used to fabricate radiation-resistant scintillating modules of dimensions 20 × 30 × 150 mm, weighing ≤0.5 kg.

Conductance data for NaNO3, KI, Pr4NBr and Bu4NI in N,N-dimethylformamide (DMF) at − 40, − 35, − 25, − 15, − 5, 5, 15, 25, 35 and 45°C are reported. The data have been analysed by the Lee–Wheaton conductance equation in terms of the limiting molar conductance (Λ0) and association constant (KA). Evaluation of single ionic conductances has been carried out on these data and on preceding experimental conductance data for MBr (M = Na+, K+, Cs+, NH4+, Et4N+, Pr4N+, Ph4P+), KClO4, NaBPh4 , Ph4PCl and Bu4NBPh4 using the Walden product of Bu4N+. The temperature dependences of Λ0 and KA are discussed. The values of KA indicate that all these salts are weakly associated in DMF.

AlN growth in a low-scale production AIX2000HT MOVPE system was studied. The dependence of the growth rate on ammonia flow was shown to be of a threshold nature originating from gas-phase parasitic reactions. An AlN growth rate up to 8.6 μm/h under optimized reactor conditions was demonstrated.

A new method of forming the active region in high-efficiency InGaN/GaN/AlGaN light-emitting diode (LED) structure for long-wave green range is described. The introduction of a short-period InGaN/GaN superlattice situated immediately under the emitting quantum well and overgrown with GaN layer at reduced temperature leads to a more than tenfold increase in the efficiency of emission. For the proposed LEDs, the maximum quantum efficiency was 12% at 552 nm and 8% at 560 nm.

High-frequency ultrasound has been shown to accelerate enzymatic fibrinolysis. One of the supposed mechanisms of this effect is the enhancement of mass transport by acoustic streaming, i.e., ultrasound-induced macroscopic flow around the clot. In this study, which is aimed at further elucidating the mechanisms of the acceleration of fibrinolysis by ultrasound, we investigated whether ultrasound would accelerate fibrinolysis if the flow around the thrombus is already present, as may occur in vivo. The effect of the ultrasound-induced temperature rise was also studied. In a model of a plasma clot submerged in plasma, containing tissue-type plasminogen activator, mild stirring of the outer plasma producing a shear rate of 40 seconds-1 at the surface of the clot resulted in a two-fold acceleration of lysis. A similar effect was obtained with ultrasound (1 MHz, 2 W/cm2). Furthermore, if ultrasound was applied together with stirring, only 30% acceleration by ultrasound was documented, fully attributable to the concomitant temperature rise. In a model with tissue-type plasminogen activator incorporated throughout a plasma clot, the effect of ultrasound (two-fold shortening of lysis time) was fully attributable to the concomitant temperature rise of a few degrees. We concluded that the acceleration of enzymatic plasma clot lysis by high-frequency ultrasound in the models we used can be largely explained by a combination of the effects of heating and acoustic streaming, equivalent to mild stirring. The thermal effects can hardly be utilized in vivo due to the danger of tissue overheat. The therapeutic advantage of transcutaneous high-frequency ultrasound as an adjunct to thrombolytic therapy may appear limited to the situations where there is no flow in the direct environment of the thrombus. Copyright (C) 2000 Elsevier Science Ltd. Chemicals/CAS: Tissue Plasminogen Activator, EC 3.4.21.68

Coherent ultrathin GaAsN insertions are formed in a GaN matrix by predeposition of an ultrathin GaAs layer on a GaN surface, followed by annealing in an NH3 atmosphere and overgrowth with GaN. During the overgrowth, most of the As atoms are substituted by N, with a dense array of coherent GaAsN nanodomains with lateral sizes of about 3-4 nm formed in the GaN matrix. We report a green luminescence due to GaAsN insertions, surviving at high observation temperatures and excitation densities.

We report on experimental and theoretical studies on a new type of quantum-dot (QD) structures obtained using ultrathin, i.e. below the critical thickness for 2D‐3D transition, strained narrow gap insertions in wide bandgap matrices. We concentrate on submonolayer (SML) or slightly above 1 ML CdSe insertions in a wide-gap II‐VI matrices and give the first results on ultrathin InGaN insertions in a GaN matrix. A discussion on detailed comparison of our original results with the results of other authors is presented. The formation of dense arrays (up to 10 12 cm 22 ) of nanoscale two-dimensional (2D) islands is revealed in processed high-resolution transmission electron microscopy images. In the case of stacked sheets of SML insertions, the islands in the neighboring sheets are formed predominantly in correlated or anticorrelated way for thinner and thicker spacer layers, respectively. Different polarization of photoluminescence (PL) emission recorded in edge geometry for vertically-uncoupled and coupled QDs confirms the QD nature of excitons. By monitoring of sharp lines due to single QDs using cathodoluminescence the 3D confinement is manifested. We demonstrate significant squeezing of the QD exciton wavefunction in the lateral direction using magneto-optical experiments. We point to complete suppression of lateral motion of excitons bound to islands in case of wide-gap (ZnMgSSe) matrices, as follows from PL excitation studies. A resonant (0-phonon) lasing is observed in ultrathin CdSe insertions and proves the lifting of the k-selection rule for QD excitons. We show that lack of exciton screening in QDs up to high excitation densities enables strong resonant modulation of the refractive index in stacked ultrathin insertions and allows realization of resonant (excitonic) waveguiding and lasing. This enables the realization of a new type of heterostructure laser operating without external optical confinement by layers having lower average refractive indices. Ultrahigh QD excitonic gain in dense arrays of stacked QDs allows a new type of surface-emitting laser. q 2000 Elsevier Science S.A. All rights reserved.

An experimental-computational method is developed to study the stress state of a material on the basis of its experimental kinematic diagram by using the techniques of visioplasticity. The method of R-functions and the method of stress functions are used in calculating the stress state. Volumetric plastic deformation is also taken into account. The stress field for the initial (nonsteady) stage of extrusion of an axisymmetric porous semifinished product is obtained.

SummaryFibrinolysis initially generates channels in an occluding thombus which results in blood flow through the thrombus. Since the impact of flow along the surface of a thrombus on thrombolysis has not been investigated in detail, we studied in vitro how such a flow affects lysis. Compacted and noncompacted plasma clots were used as model thrombi. With compacted clots, fibrin-specific lysis induced by alteplase in the outer plasma was accelerated about 2-fold by strong flow (arterial shear rate). Non-fibrin-specific lysis induced either by a high concentration of alteplase or by streptokinase was slow, was accompanied by rapid depletion of plasminogen in the outer plasma, and was only slightly accelerated by flow. With noncompacted clots, similar acceleration factors were documented, when mild flow (venous shear rate) was applied. Strong flow further accelerated fibrin-specific lysis, up to 10-fold as compared to lysis without flow, but paradoxically retarded non-fibrin-specific lysis. The data suggest that flow accelerates lysis by enhancing transport of plasminogen from the outer plasma to the surface of the clot. Both opposite effects of the strong flow were mediated by forceful intrusion of the outer plasma into the noncompacted clot due to flow irregularities. In the case of non-fibrin-specific lysis this resulted in the replacement of the plasminogen-containing milieu by plasminogen-depleted outer plasma in certain areas of the clot turning them into virtually unlysable fragments. This flow-enforced “plasminogen steal” may contribute to the relatively high percentage of incomplete thrombolysis (TIMI-2 grade flow) documented in a number of trials for non-fibrin-specific thrombolytic agents. In the case of fibrin-specific lysis, the effect of flow on the speed of fibrinolysis is always beneficial.

Comparative results of experiments on the ion-cyclotron resonance (ICR) heating of plasma in the Globus-M spherical tokamak using a hydrogen-deuterium mixture are presented. The experimental data are analyzed over a long period of time during which the internal surface of the chamber walls was gradually coated with graphite plates. The observed monotonic decrease in the efficiency of ICR plasma heating in the chamber with increasing graphite coverage can be explained by a growth in the high-frequency power absorption in the coating material. Results of numerical simulation of this process are reported.

A definition is given of relative information and its place in a priori information is indicated. Methods are considered for obtaining relative information concerning the reliability of the components of a system and the possibility is assessed of taking it into account when planning tests. A two-stage expert evaluation procedure is proposed for obtaining relative information.

AxGa1–xN epilayers with x = (0.07 to 0.13) were grown by MOCVD on AlGaN nucleation layer deposited on sapphire substrates. The epilayers grown under constant TMA and TMG flows demonstrated a nonuniform in-depth Al distribution. This effect can be suppressed by varying the TMA/(TMA + TMG) mole flow ratio during the growth and by using an AlN-coated susceptor. Photoluminescence (PL) studies revealed the so-called “S-shaped” PL maximum energy shift with increase in the temperature of observation. Rapid thermal annealing at 1100 to 1300 °C for 30 to 120 s resulted in a complete suppression of this behavior and the PL maximum energy was shifted towards the higher-energy side of the spectrum by more than 20 meV. The room-temperature electron mobility was increased from 30 to 40 cm2 V–1 s–1 for the as-grown samples to 200 cm2V–1s–1 for the annealed samples without significant change in the electron concentration (1.0 to 1.5) × 1018 cm–3.

It is known that the critical temperature T c of ultrathin YBCO films is reduced to values far less than 77 K. To improve the superconducting properties of ultrathin YBCO films, we developed a new buffer layer which allowed an increase in the critical temperature of five-unit-cell-thick YBCO films to values above 77 K. Using atomic force microscopy (AFM) to study the growth modes of ultrathin YBCO films deposited on a SrTiO 3 substrate and on a YBaCuNbO buffer layer, we found that ultrathin YBCO films deposited on a SrTiO 3 substrate are formed due to 2D nucleation. The growth of ultrathin YBCO films deposited on YBaCuNbO buffer is governed by the step-flow mode. As a consequence of the different growth modes, the ultrathin films deposited on a SrTiO 3 substrate and a YBaCuNbO buffer layer have different surface morphologies and superconductive properties. We believe that the step-flow mode makes it possible to improve the ultrathin YBCO film structure and increase the critical temperature.

The main parameters and design of the Globus-M spherical tokamak are described, including the modifications introduced after construction was completed. The experimental program and possibilities for optimizing the operating regimes of the facility are discussed. The research program envisages beginning with Ohmic heating experiments and continuing with work on rf heating and generation of drag currents. Recent results of modeling the propagation of rf waves in the 10–50 MHz and 2.45 GHz ranges are presented and the possibility of using these to control the profiles of the plasma parameters is discussed. A brief description is given of the primary diagnostics and the further development of the diagnostic complex is discussed.

Lasing is discovered in the direction perpendicular to the surface in quantum-size InGaN/GaN multilayer heterostructures grown by vapor-phase epitaxy. At high excitation densities one of the modes in the luminescence spectrum, which is modulated by modes of the Fabry-Perot cavity formed by the GaN/air and GaN/sapphire-substrate interfaces, is sharply amplified and begins to dominate the spectrum. The dependence of the luminescence intensity on pump density has a clearly expressed threshold character. The threshold excitation density in the vertical direction is 5–6 times greater than the stimulated-emission threshold for observation from an end surface of the structure. The gain coefficient in the active region at the threshold for surface-emitting lasing is estimated as 2×105 cm−1. The interaction between the cavity modes and the gain spectrum is detected in the form of displacement (by up to 2.6 nm) of modes on the short-wavelength edge of the luminescence spectrum toward higher photon nergies. The characteristic temperature (T0) measured in the range from 16 to 120 K is 480 K. At higher temperatures T0 K.

Semiconductor heterostructures with vertical optical cavities with active regions, based on arrays of InAs quantum dots inserted in an external InGaAs quantum well, have been obtained by molecular-beam epitaxy on GaAs substrates. The dependences of the reflection and photoluminescence spectra on the structural characteristics of the active region and optical cavities have been investigated. The proposed heterostructures are potentially suitable for optoelectronic devices at wavelengths near 1.3 µm.

SummaryIn a number of cases, thrombolytic therapy fails to re-open occluded blood vessels, possibly due to the occurrence of thrombi resistant to lysis. We investigated in vitro how the lysis of hardly lysable model thrombi depends on the choice of the plasminogen activator (PA) and is accelerated by ultrasonic irradiation. Lysis of compacted crosslinked human plasma clots was measured after addition of nine different PAs to the surrounding plasma and the effect of 3 MHz ultrasound on the speed of lysis was assessed.Fibrin-specific PAs showed bell-shaped dose-response curves of varying width and height. PAs with improved fibrin-specificity (staphylokinase, the TNK variant of tissue-type PA [tPA], and the PA from the saliva of the Desmodus rotundus bat) induced rapid lysis in concentration ranges (80-, 260-, and 3,500-fold ranges, respectively) much wider than that for tPA (a 35-fold range). However, in terms of speed of lysis, these three PAs exceeded tPA only slightly. Reteplase and single-chain urokinase were comparable to tPA, whereas two-chain urokinase, anistreplase, and streptokinase were inferior to tPA. In the case of fibrin-specific PAs, ultrasonic treatment accelerated lysis about 1.5-fold. For streptokinase no acceleration was observed. The effect of ultrasound correlated with the presence of plasminogen in the outer plasma, suggesting that it was mediated by facilitating the transport of plasminogen to the surface of the clot.In conclusion, PAs with improved fibrin-specificity induce rapid lysis of plasminogen-poor compacted plasma clots in much wider concentration ranges than tPA. This offers a possibility of using single-or double-bolus administration regimens for such PAs. However, it is not likely that administration of these PAs will directly cause a dramatic increase in the rate of re-opening of the occluded arteries since they are only moderately superior to tPA in terms of maximal speed of lysis. Application of high-frequency ultrasound as an adjunct to thrombolytic therapy may increase the treatment efficiency, particularly in conjunction with fibrin-specific PAs.

We report a method of profiled sapphire substrate preparation and growth of InGaAlN light-emitting diode (LED) structures over these substrates. Sapphire substrates with textured front surface were prepared by the simple method of nanoscale gold drops formation on sapphire surface followed by etching in hot H3PO4 acid. Comparison of blue LEDs grown on standard (flat) and profiled sapphire substrates in one epitaxial process shows significant increase in output power due to increased light extraction without deterioration of other LED characteristics.

One of the main factors that limit the maximum attainable efficiency of InGaAlN-based light-emitting diode (LED) structures grown on standard sapphire substrates is the low efficacy of extracting light from devices. A promising solution of this problem consists in using specially profiled (patterned) sapphire substrates. A method for the formation of a special surface microrelief on the sapphire substrates is described. The properties of GaN epilayers and InGaAlN-based LED heterostructures grown on such substrates are presented.

Stimulated emission is studied in a hexagonal AlGaN/GaN/AlGaN double heterostructure grown on a (0 0 0 1) sapphire substrate by low pressure (200 mbar) metallorganic vapor phase epitaxy. A sharp increase in the edge emitted luminescence intensity is obtained above a threshold excitation density of 40 kW/cm2 and is accompanied by a strong narrowing of the luminescence line width. The specific surface morphology of the heterostructure is suspected to be responsible for an optical feedback in the sample. Although the surface is extremely smooth yielding roughness values of σRMS

We have proposed and realized a new type of optoelectronic structures we refer to as excitonic waveguides which allow an ultimate shift towards the violet spectral range (460 nm at 300 K for the ZnMgSSe/GaAs materials system). The excitonic waveguiding effect is realized at the low energy side of the strong exciton absorption peak due to localized states, caused by ultrathin narrow-gap insertions. To realize the zero-phonon lasing mechanism resonant to the spectral region of resonantly enhanced refractive index one needs to break the k-selection rule preventing direct radiate exciton recombination having large in-plane k-vector dominating at high excitation densities and observation temperatures. This can be done by localizing excitons at nanoscale CdSe-rich islands formed by ultrathin CdSe insertions.

Polarized Raman spectra of lanthanum borogermanate (LBG) glasses of different compositions, as well as of LBG glasses obtained by the hot-extrusion technique, have been obtained. In addition, the crystallization behaviour of LBG glasses of different compositions has been studied by differential thermal analysis and X-ray diffraction. Both the Raman spectra profile and the crystallization behaviour depend on the lanthanum–boron ratio. Polarized Raman spectra of hot-extruded samples show differences from the unextruded samples. For the first time, structural changes in glasses under hot-extrusion treatment were observed by vibrational spectroscopy.

The possibility of locally varying the potential energy of the electrons and holes localized in a quantum well by a quantum-dot array deposited in the immediate vicinity of the quantum well is demonstrated. These changes in the potential energy are induced when a strain arises in the quantum-dot region.

Photoluminescence (PL) of n-InN grown by molecular beam epitaxy with Hall concentrations from 3.6 to 7.3 × 1017 cm–3 demonstrates dependences on carrier concentration, temperature, and excitation density which give evidences of a fast energy relaxation rate of photoholes and their equilibrium distribution over localized states. The structure of the PL spectra observed at 4.2 and 77 K in the energy interval from 0.50 to 0.67 eV indicates that a considerable part of holes is trapped by deep and shallow acceptors before the interband recombi- nation with degenerate electrons occurs. At room temperature, the band-to-band recombination of free holes and electrons dominates in PL. Experimental results on PL and absorption are described by model calculations under the assumptions of a band gap equal to 0.665–0.670 eV at zero temperature and zero carrier concentration and a non-parabolic conduction band with the effective mass at the G-point equal to 0.07 of the free electron mass. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This contribution presents recent results obtained with a pyroelectric bolometer installed on the Globus-M spherical tokamak. By results of processing signals, the information about a time lag between signals of different channels was received, using a correlation analysis. This part of work is aimed to estimate a velocity of macroscopic movements of radiation sources. Radiation losses during recent experiments with NBI and ICRH operation are presented and considered as well.

The targeted plasma parameters of the compact spherical tokamak (ST) Globus-M have basically been achieved. The reasons that prevent further extension of the operating space are discussed. The operational limits of Globus-M together with an understanding of the limiting reasons form the basis for defining the design requirements for the next-step, Globus-M2. The recent experimental and theoretical results achieved with Globus-M are discussed, the operational problems and the research programme are summarized and finally, the targeted Globus-M2 parameters are presented. The magnetic field and plasma current in Globus-M2 will be increased to 1?T and 0.5?MA, respectively. The plasma dimensions will remain unchanged. With auxiliary heating at a high average plasma density, the temperatures will be in the keV range and the collisionality parameter with ?*???1 will define the operational conditions. Noninductive current drive will be a major element of the programme. The engineering design issues of Globus-M2 tokamak are discussed and the technical tokamak parameters are confirmed by thermal load and stress analysis simulations. The experimental results obtained on Globus-M2 and the limits of its performance should clarify the feasibility of an ST-based super compact neutron source.

Spontaneous emission of terahertz radiation from modulation-doped AlGaN/GaN heterostructure under conditions of heating of a two-dimensional electron gas in the lateral electric field has been studied. The experimental data on the field dependence of the integral intensity of THz emission is compared with the theoretical simulation of blackbody-like emission from hot 2D electrons. Complementary transport measurements have been carried out to determine the dependence of effective electron temperature on electric field.

Binding of components of the fibrinolytic system to fibrin is important for the regulation of fibrinolysis. In this study, decomposition of the fibrin network and binding of plasminogen and plasminogen activators (PAs) to fibrin during lysis of a plasma clot were investigated with confocal microscopy using fluorescein-labeled preparations of fibrinogen, plasminogen, tissue-type PA (t-PA), and two-chain urokinase-type PA (tcu-PA). Lysis induced by PAs present throughout the plasma clot was accompanied by a gradual loss of fibrin content of fibers and by accumulation of plasminogen onto the fibers. Two sequential phases could be distinguished: a phase of prelysis, during which the fibrin network remained immobile, and a phase of final lysis, during which fibers moved with a tendency to shrink and eventually disappeared. The two phases occurred simultaneously but in different locations when lysis was induced by PAs present in the plasma surrounding the clot. The zone of final lysis was located within a 5-8-μm superficial layer, where fibers were mobile, and surface-associated fibrin agglomerates appeared. Plasminogen accumulated in these agglomerates up to 30-fold as compared with its concentration in the outer plasma. t-PA was also highly concentrated in the agglomerates, and tcu-PA bound to them slightly. The zone of prelysis, where plasminogen was moderately accumulated on the immobile fibers, was located deeper in the clot. This zone was much thinner in the case of t-PA-induced lysis than in the case of tcu-PA-induced lysis, reflecting the difference in penetration of the two PAs into the clot. We conclude that under conditions of diffusional transport of fibrinolytic enzymes from outside a plasma clot, extensive lysis is spatially restricted to a zone not exceeding 5-8 μm from the clot surface. In this zone the structure of the fibrin network undergoes significant changes, and strikingly high accumulation of fibrinolytic components takes place.

Specific features of MOCVD growth of AlGaN/GaN heterostructures have been studied. In the structures obtained, the 2D electron gas in the channel had a density of 1.2×1013 cm−2 and a mobility of 1290 cm2/(V s) at room temperature. The effect of the purity of starting components on the properties of the structure is studied.

We present the results of the first experiments on the HF heating of hydrogen-deuterium plasma at ion cyclotron frequencies in the Globus-M spherical tokamak. A power of 200 kW at a frequency of 9.1 MHz introduced via a single-loop antenna led to an increase in the ion temperature from 170 to 300 eV. Characteristic times of the ion temperature buildup and decay corresponded to the ion energy confinement time in the tokamak plasma.

Background Binding of plasminogen to partially degraded fibrin is an important step in fibrinolysis, influencing its rate and fibrin specificity. Little is known about the spatial distribution of plasminogen and of plasminogen-binding sites inside thrombi during lysis. In the present study, we investigated this problem, which is important for a better understanding of the local regulation of fibrinolysis and the rate-limiting factors of therapeutic thrombolysis. Methods and Results An experimental system was used that allowed continuous visualization and quantification by fluorescence microscopy of the spatial distribution of fluorescein-labeled plasminogen inside and outside model thrombi. Strong superficial accumulation of plasminogen was observed during lysis of a plasma clot induced by tissue-type or urokinase-type plasminogen activators in the surrounding plasma. A distinctly visible plasminogen-accumulating shell moved continuously with the reducing surface of the clot. The accumulation decreased in conditions of exhaustive activation of plasminogen in the outer plasma. It was found in a purified system that a thin superficial layer (≈50 μm wide) of a plasmin-treated fibrin clot exposes about 2.5 plasminogen-binding sites per fibrin monomer with a K d of 2.2 μmol/L. At a physiological concentration of plasminogen (1.5 μmol/L) in the outer medium, plasminogen was concentrated about 10-fold in this layer. The binding was dose-dependently inhibited by ε-aminocaproic acid. Conclusions We conclude that the generation of potent surface-associated plasminogen-binding sites during thrombolysis results in a strikingly high plasminogen concentration at the dynamically changing surface of a lysing clot. The necessity of a continuous plasminogen supply from the plasma supports the use of fibrin-specific and plasminogen-sparing agents for thrombolytic therapy.

The results of development of InAlN/AlN/GaN heterostructures, grown on sapphire substrates by metal-organic chemical vapour deposition, and high electron mobility transistors (HEMTs) based on them are presented. The dependencies of the InAlN/AlN/GaN heterostructure properties on epitaxial growth conditions were investigated. The optimal indium content and InAlN barrier layer thicknesses of the heterostructures for HEMT s were determined. The possibility to improve the characteristics of HEMTs by in-situ passivation by Si3N4 thin protective layer deposited in the same epitaxial process was demonstrated. The InAlN/AlN/GaN heterostructure grown on sapphire substrate with diameter of 100 mm were obtained with sufficiently uniform distribution of sheet resistance. The HEMTs with saturation current of 1600 mA/mm and transconductance of 230 mS/mm are demonstrated.

The obtained results demonstrate that the improvement of nanomaterial arrangement in AlGaN/GaN HEMT structures quantitatively characterized with the use of a multifractal parameter (the degree of disorder) results in the increase at several times in the electron mobility values at 2DEG channel in HEMT structures and the reliability of HEMT parameters.

The results of physical and material science and technological development of new materials of radiation photonics - nano- and microstructure of radiation-sensitive and radiation- resistant optical glass and fibers based on quartz are presented in the report. The possibility of their application in neutron diagnostics devices of nuclear power objects are considered. Component and construction options for the radiation-sensitive fiber and glass materials (with isotopes 10B, 6Li, Gd, ions of Nd3+, Ce3+ etc.), in which radiation resistance is achieved through the organization of areas of "drain" and annihilation of radiation-induced defects are considered.

We report on the first measurement of the absolute values of radiative losses in the Globus-M spherical tokamak. Measured by a wide-aperture pyroelectric bolometer, the radiative losses amount to about 30% of the total power deposited in the discharge, which is indicative of a sufficiently high purity of plasma in the experimental setup. Radiative losses on such a level have to be taken into account in determining the energy confinement time of the tokamak plasma. A new method is proposed for calibrating the bolometer using the data of other diagnostic techniques for the current ramp up stage, which provides for a coincidence up to within 15% with the calibration data obtained on a test bench.

International audience; The results of studies of the properties of composite InGaN/GaN/InAlN heterostructures are reported. It is shown that, in the InAlN layer, there is substantial phase separation that brings about the formation of three-dimensional islands consisting of AlN-InAlN-AlN regions. The dimensions of these islands depend on the thickness of the InAlN layer and the conditions of epitaxial growth. Interruptions in the growth of InAlN provide a means for influencing the structural properties of the InAlN islands. The use of composite InGaN/GaN/InAlN heterostructures, in which the InGaN layer with a high In content serves as the active region in light-emitting diode structures, makes it possible to achieve emission in the yellow-red wavelength range 560–620 nm.

International audience; InGaN/(Al,Ga)N heterostructures containing ultrathin InGaN layers, grown by submonolayer deposition are studied. It is shown that significant phase separation with the formation of local In-enriched regions ∼3–4 nm in height and ∼5–8 nm in lateral size is observed in InGaN layers in the case of InGaN and GaN growth by cyclic deposition to effective thicknesses of less than one monolayer. The effect of growth interruption in a hydrogen-containing atmosphere during submonolayer growth on the structural and optical properties of InGaN/(Al,Ga)N heterostructures is studied. It is shown that these interruptions stimulate phase separation. It is also shown that the formation of In-enriched regions can be controlled by varying the effective InGaN and GaN thicknesses in the submonolayer deposition cycles.

International audience; The results of investigations of monolithic white InGaAlN LEDs with an active region containing several thin InGaN layers, emitting in the range from blue to yellow-green, and separated by short-period InGaN/GaN superlattices, are presented. The influence of the growth conditions and layer sequence in the active region on the optical properties of monolithic white LEDs was studied with the aim of controlling their color parameters.

Different methods of stimulation of phase separation in an InGaN QWs by technological methods and by design of structure were investigated. Effect of admixing of hydrogen during growth interruptions (GIs) after deposition of the InGaN QWs on their structural and optical properties and properties of InGaN-based LEDs was investigated. Effect of growth pressure on the phase separation was investigated and formation of separate InGaN islands at increase in growth pressure was revealed. It was shown that the phase separation is stumulated in composite InAlN/GaN/InGaN heterostructures and formation of well isolated InGaN islands was observed. Effect of the phase separation on the properties of the blue and deep green LEDs was investigated and strong changes in the spectral position and current dependence of the quantum efficiency were revealed. It was shown that formation of the island due to the phase separation allows control position and width of the emission line and maximum in current dependence of the quantum efficiency. Monolithic white LEDs are containing in active region blue and green InGaN QWs grown with applying of the GIs and emitting in spectral range from 440 nm to 560 nm were studied. Monolithic white LEDs having optimal design of active region demonstrate CCT in the range of 9000-12000 K and maximal external quantum efficiency up to 14 lm/W. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The influence of different growth conditions on the In distribution in ultrathin InGaN insertions in a GaN matrix is investigated by high-resolution transmission electron microscopy and an appropriate image evaluation technique. It is demonstrated that the indium distribution represents dense arrays of In-rich nanodomains inserted in a layer with a lower indium concentration. The sizes of the In-rich regions are about 4–5 nm at a growth temperature of 720 °C. Increasing the growth temperature leads to a strong decrease in the of nanoisland density and, also, a moderate decrease in their lateral size. Increasing the trimethylindium/trimethylgallium ratio strongly increases the density of the islands, but the lateral size remains weakly effected. The observations are in agreement with a thermodynamic model of island formation including entropy effects.